It seems logical that these might have been used to feed babies, but the article also says it was previously thought they could have been used to feed sick or elderly. The only justification given for assuming it was a baby was not from the data, but that "Sometimes research on women tends to be a little bit marginalized..." That is very much true, but it does not definitively mean these were baby bottles, it means the possibility may not have been considered previously due to a research bias.